1. Field of the Invention
The invention relates to the field of lighting devices, in particular for automotive vehicles.
2. Description of the Related Art
It is necessary, in particular for nighttime driving, to provide the drivers of vehicles with lighting that matches as best as possible the traffic conditions, in order to decrease the risk of accidents. In particular, it is important for the driver to be able to have an optimal vision of the road lying in front of him and the sides of this road, without however dazzling other drivers or pedestrians.
Automotive vehicles include devices for lighting the road, which devices are used in case of insufficient visibility, for example in the evening, at night or during periods of bad weather. Conventionally, modern automotive vehicles are able to provide a number of types of lighting, and in particular:
what is called “high beam” lighting, produced by means of lighting devices that emit a light beam directed toward the horizon, and that lights the road scene integrally over a long distance of about 200 meters;
what is called “low beam” lighting, produced by means of low-beam or dipped lighting devices that emit a light beam bounded by an upper cut-off plane, inclined downward by about 15° to the horizontal, giving the driver a visibility over a distance of about 60 to 80 meters; the aim of this downward-sloping upper cut-off is to prevent other users present in the road scene extending in front of the vehicle, or on the sides of the road, from being dazzled; and
what is called “fog” lighting, used in case of reduced visibility and produced by means of lighting devices that emit a beam of short range, of about 40 meters, which beam is limited toward the top by a cut-off plane but of substantial lateral spread, and does not emit upward rays liable to give rise to undesirable interactions with the droplets of fog, in order to allow the driver to take in his immediate environment.
The lighting devices just mentioned, and more particularly those that are used as low-beam lights, produce light beams that are perfectible when these headlamp devices are used under certain conditions. New functions, designated advanced functions and grouped under the acronym AFS (for advanced front lighting systems), which especially provide other types of beam, have therefore been developed. It is especially a question of:
a function called a BL (bending light) function, which may be decomposed into a function called a DBL (dynamic bending light) function and a function called an FBL (fixed bending light) function. These bending light functions are used when turning corners and are produced by means of headlamps that emit a light beam the horizontal orientation of which varies when the vehicle is following a curved path, so as to correctly illuminate the road sections that are going to be driven over by the vehicle and that are located, not on the axis of the vehicle, but in the direction that the vehicle is on the point of taking as a result of the angle transmitted to the steered wheels of the vehicle by its driver;
a function called a “town light” function; this function widens a low-beam light beam while slightly decreasing its range;
a function called a “motorway light” function. This function increases the range of a low-beam light while concentrating the light flux of the low-beam light on the optical axis of the headlamp device in question;
a function called an “overhead light” function; this function modifies a low-beam light beam so that sign gantries located above the road are illuminated satisfactorily by means of the low-beam lights; and
a function called an AWL (adverse weather light) function; this function modifies a low-beam light beam such that the driver of a vehicle driving in the opposite direction is not dazzled by the reflection of the light from the headlamps on a wet road.
In addition, when the low-beam lighting is in operation the pitch angle of the vehicle may undergo relatively substantial variations, depending for example on the load of the vehicle and its acceleration or deceleration, which variations cause the inclination of the upper cut-off of the beam to vary, this causing other drivers to be dazzled if the cut-off is raised, or the road to be insufficiently lit if the cut-off is lowered. It is thus known to use a manually or automatically controlled range corrector to correct the orientation of the low-beam headlamps.
Excluding high-beam lighting, the other types of lighting, in which the light beam is sloped downwards, provide only reduced visibility to the driver of the vehicle, in front of the vehicle. These types of lighting are therefore often insufficient to allow the driver to perceive all of the road scene and anticipate possible obstacles or potentially dangerous situations.
To mitigate this drawback, light beam emitting lighting devices have been developed that provide the driver of the vehicle equipped with these lighting devices with lighting comparable to that of high-beam lighting, but in which zones of shadow are created in directions in which it is not desirable to emit light, for example in directions in which vehicles have been detected, in order not to dazzle drivers.
These light beams, known as “matrix beams” or “pixel lighting” depending on the technology used, require lighting devices of complex design, and very fine adjustments to obtain the desired result, i.e. zones of shadow both the size and direction of which are variable.
Conversely, it is known to provide a lighting beam in which zones of the road scene containing notable details are illuminated with a higher light intensity than the environment of these details, in order to especially draw the attention of the driver of the vehicle to the latter.
It is thus known to integrate into a lighting device a digitized matrix-array projecting system. It is thus possible, for example via information-processing means, to project any image. This especially makes it possible to suppress the light beam emitted by the lighting device from subportions that would have the effect of dazzling people located in the field of projection of the lighting device (pedestrian, driver of a vehicle approaching in the opposite direction, etc.) but also to add information (notable details, etc.).
Controlling a digitized matrix-array projecting system requires a large amount of information. It is especially necessary to provide a complete light map. By light map what is meant is all the points (pixels) describing the projected image, which map may take the form of an electronic file comprising an image.
In a vehicle, lighting is conventionally managed by a central control system, thereby requiring a substantial stream of data to be transmitted between this central control system and the actuators of the lighting devices.
U.S. 2002/0196636 A1, which issued as U.S. Pat. No. 6,497,503 (Dassanayake et al.), describes a static projecting system that stores each light map liable to be projected. This lacks flexibility (no provision is made for context-dependent dynamic light-map modification) and requires a lot of memory.
U.S. 2012/0044090 A1, DE102006059064A1, EP1707438A1, EP1806531A1, EP2690352A1, which is equivalent to U.S. 2014/0029282 or even U.S. 2004/0052083 A1, which issued as U.S. Pat. No. 6,960,005, describes projecting systems that also lack flexibility and/or require lots of memory or bandwidth. In particular, the transmission of videos over a bus of a vehicle is liable to saturate this bus, and to not leave enough bandwidth available for other applications.